a sneaky type of poo that quickly hides in the shadowy hole in the back of the toilet so that when the person who birthed that poo turns to check, it appears there is no poo whatsoever!
Belvedere Sampsonite discovered he ninjapoo in 1708 after refusing to believe that all his pushing and groaning had been for nothing.

Abe thought someone had stolen his turd but Francis said its probably a ninjapoo.

human inertia is the force necessary to change from one state, such as watching MacGuyver escape from one more foreig prison camp with a pocket knife and an ABBA greatest hits cassette, to another state such as taking the trash out or answering the phone. Human inertia has profoundly changed the world
through repeated inaction.

Knowing he was no match for human inertia, Haans decided he would get a new cat later as opposed to getting up and letting the cat in from the blizzard.

migration time is the length of time required for a flatulent to migrate from the turdholder, out through whatever clothing is present, to be experienced by awaiting noses.---Migration time is greatly affected by types and layers of clothing. For instance, a very baggy shorts, or kilts, allow for very short migration time. It is believed that Albert Einstein's initial theory of relativity somehow involved migration time from a monks robe.

Due to Gilberto's migration time misjudgement, everyone in the elevator thought he shit his pants.